1. Field of the Invention
The present invention relates to a display control apparatus for a liquid crystal display apparatus.
2. Related Background Art
Hitherto, a cold cathode ray tube display apparatus (hereinafter, abbreviated to "CRT") has generally been used as a display apparatus which is applied to a personal computer (hereinafter, abbreviated to "PC") or a work station (hereinafter, abbreviated to "WS"). To improve the understanding by the sense of sight on the basis of the human engineering, the graphic function such as a window function or the like is expanded. A high resolution and a large display screen are needed to realize such an expanded graphic function.
On the other hand, in recent years, a liquid crystal display apparatus (hereinafter, also abbreviated to "LCD") having a TN (Twisted Nematic) or STN (Super Twisted Nematic) structure or the like has been used in a lap-top type PC or the like due to predominance of light weight and thin size according to its construction. As for the LCD having such a TN or STN structure or the like, in the case where the number of scan lines is increased to realize a high resolution, a liquid crystal material having sharp electro/optical characteristics is needed to assure a margin of a display contrast. A ferroelectric liquid crystal having bistability is known as a liquid crystal material of such an LCD.
In case of the ferroelectric liquid crystal (FLC) which is known at present, when an operation temperature is low, a flickering occurs due to its temperature characteristic because the FLC doesn't have enough high display speed in a high precision display mode. To prevent the flicking, a method of drawing by a high-order interlace (hereinafter, referred to as "multi-interlace") is known.
According to the multi-interlace drawing, when an antimation image is displayed, a flicker occurs in display modes such as pointing device, pop-up menu, scroll, and the like and a display quality is deteriorated. Therefore, to prevent such flicker of the display, a method of partially rewriting a picture plane by a non-interlace for an object which is drawn at a high speed is known.
The above partial writing method, however, is realized by using special hardware and software which are used only for the LCD. Therefore, hitherto, a display control apparatus for the LCD is installed on a mother board or an expansion slot of a host computer and is directly coupled to an address bus, a data bus, and a control signal line of a central processing unit (hereinafter, abbreviated to "CPU") of the host computer and needs a special software driver which is used only for the LCD.
As mentioned above, the display control apparatus for the conventional LCD has a problem such that it needs the special software driver.